Sure, Santorum did terribly in 2006, but Romney would have done equally bad if he had run for re-election that year, and he did do equally bad in 1994, a much more Republican year.
I'm actually pretty curious, how do you guys think Mitt would have fared had he run in 2006? I think we're all in agreement that he would have lost, but by how much?
Deval Patrick won in '06 by twenty points. As an incumbent with lots of cash to campaign with, would Mitt have closed the gap? Or was he so unpopular at the time that he would have lost by even more?